1. Field of the Invention
The present invention relates to a laser processing method for processing grooves and the like on a work by the irradiation of laser beam. The invention also relates to an ink jet recording head the grooves of which are processed by such processing method.
2. Related Background Art
In recent years, the laser oscillator is widely used as the light source of a processing apparatus. Particularly, the pulse laser oscillator of the ultraviolet region has drawn attention as the light source used for patterning ablation on polymer without development, and the oscillator of this type is utilized (as disclosed in the specifications of Japanese Patent Application Laid-Open No. 02-121845, Japanese Patent Application Laid-Open No. 04-009291, Japanese Patent Application Laid-Open No. 04-339585, Japanese Patent Application Laid-Open No. 02-121842, Japanese Patent Application Laid-Open No. 02-187346, Japanese Patent Application Laid-Open No. 03-101954, Japanese Patent Application Laid-Open No. 03-101960, and others, for example).
Also, as inventions form a laser processed solid configuration by one-processing in the direction of the laser irradiation, the inventions have been disclosed in the specifications of Japanese Patent Application Laid-Open No. 08-25639 and Japanese Patent Application Laid-Open No. 10-118782.
In recent years, however, it has been required for the ink jet recording head, which is processed by the application of the known technologies and techniques, to provide images in higher quality at higher speeds. It is, therefore, contemplated to incorporate many numbers of nozzles in higher density on an elongated head.
Under such circumstances, if it is attempted to process nozzles for use of an elongated head of as long as four inches having 360 dpi, 1,408 nozzles as disclosed in the specification of Japanese Patent Application Laid-Open No. 08-25639, for example, there is a problem encountered that the region of four inches cannot be processed at a time. Therefore, this region is divided into 11 regions each having 128 nozzles when actually processed. Then, the carbon 100 which has been created from the preceding 128 nozzles thus processed is accumulated in the following region to be processed. This accumulated carbon 100 is greater on the side nearer to the 128 nozzles that have been processed in the last step, and smaller as it is father away from such side (see FIG. 11). Here, in FIG. 11, a reference numeral 105 designates the grooves processed in the preceding step, and 106, the grooves to be processed in the next step.
Also, when the interior of each nozzle is processed three-dimensionally, the processing depth is made shallower by reducing the laser beam 102 which is incident upon the work (see FIG. 12). Therefore, the carbon created from the 128 nozzles processed in the preceding step is removed by the laser beam to process grooves before the grooves of the following 128 nozzles are processed in the next step. However, it is sometimes impossible to remove the carbon sufficiently by the application of the reduced laser beam used for processing the shallower portion. Particularly, the shallower the processing depth, the weaker becomes the force to remove carbon, because the laser beam is more reduced. As a result, it becomes difficult to perform processing in good precision due to remaining carbon (see FIG. 11).
Here, in FIG. 12, a reference numeral 108 designates the total reflection film; 109, the film having the greater transmittance for deeper processing; 110, the film having the smaller transmittance for shallower processing; 111, the member for forming extrusions; and 112, the mask.
Also, with the structure disclosed in the specification of Japanese Patent Application Laid-Open No. 10-118782, the amount of actually reduced beam tends to fluctuate depending on the finish of the light shielding pattern of the mask, which leads to the resultant variation of accuracy after processing. Usually, this variation does not exert serious influence, but it should become no longer negligible when processing the ink jet head used for the formation of more precise images in higher quality as described earlier.
Also, when the nozzle grooves are processed by the application of the laser beam, the walls remaining on the side faces of the grooves thus produced are inclined. This inclination becomes greater or smaller depending on the intensities of the energy of the laser beam (see FIG. 13). For the portion where the processing depth is shallower, that is, the energy of laser beam is made smaller due to the reduction of the amount thereof, this inclination becomes greater, and the lower face of each wall is in the form which is largely deviated to the inner side. In other words, the deep portion of each groove becomes extremely smaller. This means that when orifices are processed after the grooves are formed, the laser beam for use of drilling is blocked by the wall portions of the grooves. Then, the resultant hole configuration is subjected to irregularity, and it may become impossible to obtain the size of orifices as anticipated. As a result, the ink jet recording head thus manufactured is not suitable eventually for recording images in higher quality as desired.
The present invention is designed in consideration of these problems discussed above. It is an object of the invention to provide a laser processing method whereby to incorporate an elongated and highly precise nozzles in higher density, which is most suitable for the higher speed recording in higher image quality demanded for an ink jet recording head. It is another object of the invention to provide an ink jet recording head manufactured by such method as this.
With the provision of the following means, it is possible to attain the objectives of the invention.
In other words, the method of the present invention for manufacturing an ink jet recording head, which is provided with a ceiling plate having grooves of locally different depth to form ink paths arranged corresponding to each of plural discharge ports; and a substrate having discharge energy generating elements each arranged on a part of each of the paths, and which is structured by bonding the ceiling plate and the substrate together, comprises the steps of performing a first laser processing to process grooves of first depth by irradiating laser beam through a first mask pattern corresponding to the ink path pattern of the ceiling plate; and performing a second laser processing to form a region of locally different depth in each of the grooves by irradiating laser beam through a second mask pattern having the reduced beam pattern to be locally open on the exposure region of the first mask pattern corresponding to the grooves each having the first depth.
Also, for this method, no beam reduction pattern for reducing the laser beam is included in the first pattern.
Also, the positioning of the second mask pattern with the grooves is made to be in agreement with the inclined portions processed and formed on the walls of the grooves.
Also, the first and the second laser processing steps are performed in plural times, respectively, by deviating the positional relationship between the ceiling plate and mask in the arrangement direction of grooves so as to make the grooves adjacent to the plural grooves that have been processed.
Also, the first mask pattern and the second mask pattern are provided for one and the same mask, and the positioning of the second mask pattern with the grooves is performed by moving the mask in the direction along the ink paths.
In order to achieve the objectives of the invention, an ink jet head which is manufactured by the method described above is also provided.
With the method as referred to in the preceding paragraphs, the processing is performed up to the first depth without reducing beam. Then, it is made possible to execute processing steps in good precision without being affected by the carbon produced in the process of the adjacent nozzles.
Also, for the portions where the processing depth should change, the masks are changed to process configurations freely as desired. At the same time, by the utilization of the inclinations formed on the wall faces of the first grooves which have been processed last, the positioning is made to obtain the grooves processed in higher precision.
Also, it is possible to execute processing without being affected much by the variation of finished dimensions irrespective of the mask pattern having the reduced beam.
Also, it is arranged to process inclinations so as not to allow them to be made greater. Therefore, the orifices which should be drilled subsequently present highly precise configuration, because the beam is not blocked by the walls of the grooves, hence making it possible to provide a method for processing an elongated ink jet head for use of the formation of images in higher quality.